Nav: It's now possible to navigate sibling of a menu-bar while navigating inside one of their child. If a Left<>Right navigation request fails to find a match we forward the request to the root menu. (#787, #126)

Currently the sibling menu is isn't automatically opened, that's still left to it (and even that can be anoying in Windows when the first menu-item is a child menu)

imgui.cpp

@@ -2634,6 +2634,15 @@ static void NavUpdate()
         g.NavMoveFromClampedRefRect = false;
     }
 
+    // When a forwarded move request failed, we restore the highlight that we disabled during the forward frame
+    if (g.NavMoveRequestForwardStep == 2)
+    {
+        IM_ASSERT(g.NavMoveRequest);
+        if (g.NavMoveResultId == 0)
+            g.NavDisableHighlight = false;
+        g.NavMoveRequestForwardStep = 0;
+    }
+
     // Apply application mouse position movement, after we had a chance to process move request result.
     if (g.NavMousePosDirty && g.NavIdIsAlive)
     {
@@ -2781,14 +2790,24 @@ static void NavUpdate()
 
     // Initiate directional inputs request
     const int allowed_dir_flags = (g.ActiveId == 0) ? ~0 : g.ActiveIdAllowNavDirFlags;
-    g.NavMoveDir = ImGuiDir_None;
-    if (g.NavWindow && !g.NavWindowingTarget && allowed_dir_flags && !(g.NavWindow->Flags & ImGuiWindowFlags_NoNavInputs))
+    if (g.NavMoveRequestForwardStep == 0)
     {
-        if ((allowed_dir_flags & (1<<ImGuiDir_Left))  && IsNavInputPressed(ImGuiNavInput_PadLeft,  ImGuiNavReadMode_Repeat)) g.NavMoveDir = ImGuiDir_Left;
-        if ((allowed_dir_flags & (1<<ImGuiDir_Right)) && IsNavInputPressed(ImGuiNavInput_PadRight, ImGuiNavReadMode_Repeat)) g.NavMoveDir = ImGuiDir_Right;
-        if ((allowed_dir_flags & (1<<ImGuiDir_Up))    && IsNavInputPressed(ImGuiNavInput_PadUp,    ImGuiNavReadMode_Repeat)) g.NavMoveDir = ImGuiDir_Up;
-        if ((allowed_dir_flags & (1<<ImGuiDir_Down))  && IsNavInputPressed(ImGuiNavInput_PadDown,  ImGuiNavReadMode_Repeat)) g.NavMoveDir = ImGuiDir_Down;
+        g.NavMoveDir = ImGuiDir_None;
+        if (g.NavWindow && !g.NavWindowingTarget && allowed_dir_flags && !(g.NavWindow->Flags & ImGuiWindowFlags_NoNavInputs))
+        {
+            if ((allowed_dir_flags & (1<<ImGuiDir_Left))  && IsNavInputPressed(ImGuiNavInput_PadLeft,  ImGuiNavReadMode_Repeat)) g.NavMoveDir = ImGuiDir_Left;
+            if ((allowed_dir_flags & (1<<ImGuiDir_Right)) && IsNavInputPressed(ImGuiNavInput_PadRight, ImGuiNavReadMode_Repeat)) g.NavMoveDir = ImGuiDir_Right;
+            if ((allowed_dir_flags & (1<<ImGuiDir_Up))    && IsNavInputPressed(ImGuiNavInput_PadUp,    ImGuiNavReadMode_Repeat)) g.NavMoveDir = ImGuiDir_Up;
+            if ((allowed_dir_flags & (1<<ImGuiDir_Down))  && IsNavInputPressed(ImGuiNavInput_PadDown,  ImGuiNavReadMode_Repeat)) g.NavMoveDir = ImGuiDir_Down;
+        }
     }
+    else
+    {
+        IM_ASSERT(g.NavMoveDir != ImGuiDir_None);
+        IM_ASSERT(g.NavMoveRequestForwardStep == 1);
+        g.NavMoveRequestForwardStep = 2;
+    }
+
     if (g.NavMoveDir != ImGuiDir_None)
     {
         g.NavMoveRequest = true;
@@ -2834,9 +2853,10 @@ static void NavUpdate()
     // Reset search 
     g.NavMoveResultId = 0;
     g.NavMoveResultDistAxial = g.NavMoveResultDistBox = g.NavMoveResultDistCenter = FLT_MAX;
+
+    // When we have manually scrolled (without using navigation) and NavId becomes out of bounds, we clamp its bounding box (used for search) to the visible area to restart navigation within visible items
     if (g.NavMoveRequest && g.NavMoveFromClampedRefRect && g.NavLayer == 0)
     {
-        // When we have manually scrolled and NavId is out of bounds, we clamp its bounding box (used for search) to the visible area to restart navigation within visible items
         ImGuiWindow* window = g.NavWindow;
         ImRect window_rect_rel(window->InnerRect.Min - window->Pos - ImVec2(1,1), window->InnerRect.Max - window->Pos + ImVec2(1,1));
         if (!window_rect_rel.Contains(window->NavRectRel[g.NavLayer]))
@@ -5231,6 +5251,7 @@ bool ImGui::Begin(const char* name, bool* p_open, const ImVec2& size_on_first_us
         window->DC.LogLinePosY = window->DC.CursorPos.y - 9999.0f;
         window->DC.ChildWindows.resize(0);
         window->DC.LayoutType = ImGuiLayoutType_Vertical;
+        window->DC.ParentLayoutType = parent_window ? parent_window->DC.LayoutType : ImGuiLayoutType_Vertical;
         window->DC.ItemFlags = ImGuiItemFlags_Default_;
         window->DC.ItemWidth = window->ItemWidthDefault;
         window->DC.TextWrapPos = -1.0f; // disabled
@@ -9966,6 +9987,27 @@ void ImGui::EndMenuBar()
     ImGuiWindow* window = GetCurrentWindow();
     if (window->SkipItems)
         return;
+    ImGuiContext& g = *GImGui;
+
+    // When a move request within one of our child menu failed, capture the request to navigate among our siblings.
+    if (g.NavMoveRequest && g.NavMoveResultId == 0 && (g.NavMoveDir == ImGuiDir_Left || g.NavMoveDir == ImGuiDir_Right))
+    {
+        ImGuiWindow* nav_earliest_child = g.NavWindow;
+        while (nav_earliest_child->ParentWindow && (nav_earliest_child->ParentWindow->Flags & ImGuiWindowFlags_ChildMenu))
+            nav_earliest_child = nav_earliest_child->ParentWindow;
+        if (nav_earliest_child->ParentWindow == window && nav_earliest_child->DC.ParentLayoutType == ImGuiLayoutType_Horizontal && g.NavMoveRequestForwardStep == 0)
+        {
+            // To do so we claim focus back, restore NavId and then process the movement request for yet another frame.
+            // This involve a one-frame delay which isn't very problematic in this situation. We could remove it by scoring in advance for multiple window (probably not worth the hassle/cost)
+            IM_ASSERT(window->DC.NavLayerActiveMaskNext & 0x02); // Sanity check
+            FocusWindow(window);
+            SetNavIdAndMoveMouse(window->NavLastIds[1], 1, window->NavRectRel[1]);
+            g.NavLayer = 1;
+            g.NavDisableHighlight = true; // Hide highlight for the current frame so we don't see the intermediary selection.
+            g.NavMoveRequest = false;
+            g.NavMoveRequestForwardStep = 1;
+        }
+    }
 
     IM_ASSERT(window->Flags & ImGuiWindowFlags_MenuBar);
     IM_ASSERT(window->DC.MenuBarAppending);

imgui_internal.h

@@ -473,8 +473,9 @@ struct ImGuiContext
     ImGuiID                 NavInitDefaultResultId;
     ImRect                  NavInitDefaultResultRectRel;
     bool                    NavInitDefaultResultExplicit;       // Whether the result was explicitly requested with SetItemDefaultFocus()
-    bool                    NavMoveRequest;                     // Move request for this frame
     bool                    NavMoveFromClampedRefRect;          // Set by manual scrolling, if we scroll to a point where NavId isn't visible we reset navigation from visible items
+    bool                    NavMoveRequest;                     // Move request for this frame
+    int                     NavMoveRequestForwardStep;          // 0: no forward, 1: forward request, 2: forward result
     ImGuiDir                NavMoveDir;                         // West/East/North/South
     ImGuiDir                NavMoveDirLast;                     //
     ImGuiID                 NavMoveResultId;                    // Best move request candidate
@@ -585,6 +586,7 @@ struct ImGuiContext
         NavInitDefaultResultExplicit = false;
         NavMoveFromClampedRefRect = false;
         NavMoveRequest = false;
+        NavMoveRequestForwardStep = 0;
         NavMoveDir = NavMoveDirLast = ImGuiDir_None;
         NavMoveResultId = 0;
         NavMoveResultDistBox = NavMoveResultDistCenter = NavMoveResultDistAxial = 0.0f;
@@ -663,8 +665,8 @@ struct IMGUI_API ImGuiDrawContext
     ImGuiID                 LastItemId;
     ImRect                  LastItemRect;
     bool                    LastItemRectHoveredRect;
-    bool                    NavHasScroll;                   // Set when scrolling can be used (ScrollMax > 0.0f)
-    int                     NavLayerCurrent;                // Current layer, 0..31 (we currently only use 0..1)
+    bool                    NavHasScroll;           // Set when scrolling can be used (ScrollMax > 0.0f)
+    int                     NavLayerCurrent;        // Current layer, 0..31 (we currently only use 0..1)
     int                     NavLayerActiveMask;     // Which layer have been written to (result from previous frame)
     int                     NavLayerActiveMaskNext; // Which layer have been written to (buffer for current frame)
     bool                    MenuBarAppending;       // FIXME: Remove this
@@ -672,6 +674,7 @@ struct IMGUI_API ImGuiDrawContext
     ImVector<ImGuiWindow*>  ChildWindows;
     ImGuiStorage*           StateStorage;
     ImGuiLayoutType         LayoutType;
+    ImGuiLayoutType         ParentLayoutType;       // Layout type of parent window at the time of Begin()
 
     // We store the current settings outside of the vectors to increase memory locality (reduce cache misses). The vectors are rarely modified. Also it allows us to not heap allocate for short-lived windows which are not using those settings.
     ImGuiItemFlags          ItemFlags;              // == ItemFlagsStack.back() [empty == ImGuiItemFlags_Default]
@@ -714,7 +717,7 @@ struct IMGUI_API ImGuiDrawContext
         MenuBarAppending = false;
         MenuBarOffsetX = 0.0f;
         StateStorage = NULL;
-        LayoutType = ImGuiLayoutType_Vertical;
+        LayoutType = ParentLayoutType = ImGuiLayoutType_Vertical;
         ItemWidth = 0.0f;
         ItemFlags = ImGuiItemFlags_Default_;
         TextWrapPos = -1.0f;